Yeah, it'd be pretty easy to write Bale's Batman back into a DCU continuity. The only thing really preventing it from happening at this point is Nolan wanting his story to be left alone. We already know Bale would return if Nolan came to him with another story and I'm sure Snyder would relish the privilege of using such an iconic and revered version of the character. Goyer I'm not 100% sure about, but I could see him being into it too if he had the go-ahead from Nolan.

And seeing as it's being reported that (potential Man of Steel spoiler) the Wayne Enterprises logo shown in Man of Steel is in fact the Nolanverse one, they've already planted a seed in the off-chance that Nolan does change his mind down the road.

I'm not expecting it to happen, and I've heard and understand all the reasons why it's most likely a bad idea. But if that was the direction everyone wanted to move in and they were committed to it, it could be done well and it would be gargantuan.